Device for locating an impact against a transparent interactive surface

ABSTRACT

This device for locating an impact against a transparent interactive surface comprises at least three transducers distributed against the interactive surface and at least one calculator programmed to locate the impact by analysing time differences of propagation of progressive mechanical waves from the impact to the transducers on the basis of instants of impact detection identified in the electrical signals supplied by the transducers. It further comprises: a protective case, integral with the transparent interactive surface, intended to receive at least a portion of an electronic device with a display screen in such a way as to place the display screen facing the transparent interactive surface; means for adjusting the display screen for the centring thereof on a mark carried by a marking on the transparent interactive surface; and a calculator programmed to convert the location of the impact in the transparent interactive surface into a location of the impact in the display screen.

This invention relates to a device for locating an impact against a transparent interactive surface, by analysing time differences of the propagation of progressive mechanical waves propagating from the impact.

Many objects with an interactive surface are known, in particular display devices, mobile telephones or other mobile personal digital assistance devices. Their interface is in general a flat and rectangular screen with which a user can interact using a stylus or a finger. Note however that the invention applies more generally to any type of object that has an interactive surface that can propagate progressive mechanical waves from an impact, this surface not necessarily being flat, or with a rectangular contour.

The term interactive surface means a two-dimensional or three-dimensional surface, capable of changing shape in the sense of the dynamic and static elasticity of the materials when it is subjected to an impact such as a touch, a force of contact, a mechanical pulse or an impact, by thus allowing the propagation of progressive mechanical waves that can be detected using transducers, in particular surface acoustic waves, from the location of the impact. The surface deformation can be submillimetric that cannot be perceived by the unaided eye. Surfaces made from plastic, glass or metal are suitable.

Each one of the known objects with an interactive surface comprises a device for locating impacts using one or several detection techniques. It is for example known to use:

-   -   resistive techniques according to which two conductive surfaces         are brought one against the other, the locating being obtained         by an electrical contact between the two surfaces during an         impact: not only is this solution complex, but it makes the         devices fragile,     -   capacitive techniques according to which a surface accumulating         charges is sensitive to certain contacts (in particular that of         a finger) by charge transfer: this solution is also complex and         fragile, but it is furthermore insensitive to a certain number         of impacts,     -   infrared technologies, by transmission of heat or interruption         of modulated beams: this solution is complex and particularly         expensive.

A strong trend in the reduction of the manufacturing cost aims to retain only the simplest technologies that use a limited number of sensors. The invention thus relates more precisely to a device for locating that implements a technology for detecting the propagation of progressive mechanical waves in an interactive surface, in particular using detectors of the piezoelectric transducer type, based on the measurement of a difference in transit time of a wave packet generated by an impact to a plurality of piezoelectric detectors and on the deterministic calculation, using a pre-established mathematical formula, of the position of an emitting source of the wave packet. Thus, this solution requires a device for locating an impact that comprises:

-   -   an interactive surface against which are arranged and         distributed at least three transducers designed to capture the         progressive mechanical waves propagating in the interactive         surface and to transform them into electrical signals,     -   an electronic central unit, connected to the transducers in         order to receive their electrical signals,     -   a calculator programmed to identify instants of impact detection         in the electrical signals received by the electronic central         unit, and     -   a calculator programmed to locate the impact in the interactive         surface by analysing time differences of propagation of         progressive mechanical waves from the impact to the transducers         on the basis of the instants of impact detection identified.

Generally, it is as such possible to locate an impact, whether it is that of a projectile or of a stylus, since the latter is then an emitter of a pulse. In particular, this solution is well suited for leisure or sports applications involving the shooting of projectiles, the interactive surface being able to be both resistant and sensitive to the impacts. U.S. Pat. No. 6,367,800 B1 for example proposes a shooting application wherein the target itself comprises a device of this type and thus forms the interactive surface.

But the leisure or sports applications are limited, since such a resistant interactive surface does not generally allow for any interaction other than the locating of impacts. Moreover, surfaces with high interactions, in particular those of display screens of electronic devices such as mobile telephones, digital tablets, or other screens of portable or fixed computers, favour the resistive or capacitive techniques and are because of this fragile (resistive techniques) or insensitive to impacts (capacitive techniques).

Patent application US 2015/0123346 A1 proposes solutions of interactivity for a device such as the one of document U.S. Pat. No. 6,367,800 B1, such as the transmission of locating data detected by the target to an electronic device of the user, or the display of images or of videos on a computer screen arranged behind the target of which the interactive surface is then formed of a transparent material. But these solutions are of limited interactivity or are complex to implement.

It can thus be sought to design a device for locating an impact that makes it possible to overcome at least one portion of the aforementioned problems and constraints.

It is therefore proposed a device for locating an impact against a transparent interactive surface able to propagate progressive mechanical waves from the impact, comprising:

-   -   the transparent interactive surface against which are arranged         and distributed at least three transducers designed to capture         the progressive mechanical waves propagating in the transparent         interactive surface and to transform them into electrical         signals,     -   an electronic central unit, connected to the transducers in         order to receive their electrical signals,     -   a calculator programmed to identify instants of impact detection         in the electrical signals received by the electronic central         unit,     -   a calculator programmed to locate the impact in the transparent         interactive surface by analysing time differences of propagation         of progressive mechanical waves from the impact to the         transducers on the basis of the instants of impact detection         identified,     -   a protective case integral with the transparent interactive         surface and of which the interior volume is intended to receive         at least a portion of an electronic device with a display screen         in an arrangement according to which the display screen is         placed facing the transparent interactive surface, the         protective case having an opening through which said at least         one portion of the electronic device can be inserted,     -   means, integral with the protective case, for adjusting a         positioning of the display screen with respect to the         transparent interactive surface for a centring of the display         screen on a marker carried out by a marking on the transparent         interactive surface, and     -   a calculator programmed to convert the location of the impact in         the transparent interactive surface into a location of the         impact in the display screen when said at least one portion of         the electronic device is inserted into the protective case and         when the positioning of the display screen is adjusted.

Thus, the simplicity and the resistance of a device for locating an impact with progressive mechanical wave detection with the possibilities of interactivities offered by the display screen of an electronic device are combined at least cost and in complete safety. This clever combination makes it possible to imagine leisure or sports applications for the general public that would not be able to be considered otherwise.

Optionally, the protective case is shaped in such a way as to receive in its interior volume one of the elements of the set formed of a mobile telephone, a digital tablet, a flat screen support for portable computer, a keyboard support for portable computer, a monitor for computer, a television receiver and a video projector associated with a rear projection screen.

Also optionally, the transparent interactive surface is designed in a material of sufficient rigidity, in particular polycarbonate, so that the impact does not significantly affect the display screen of the electronic device when the positioning of the display screen is adjusted.

Also optionally, one of the walls of the protective case comprises the transparent interactive surface and the interior volume of the protective case is intended to receive at least the display screen of the electronic device.

Also optionally, a device for locating an impact according to the invention can comprise a closure element of the opening through which the display screen can be inserted, in particular a hermetic closure element.

Also optionally, a device for locating an impact according to the invention can comprise:

-   -   an autonomous and rechargeable source of electrical energy         integral with the protective case, or     -   means of electrical connection to the electronic device,         for an electrical power supply of the electronic central unit         which is integral with the protective case.

Also optionally:

-   -   the transparent interactive surface is designed in such a way as         to have an inclination towards the front by a non-zero angle         with respect to the vertical when the protective case is         arranged on a stable support, and     -   a receptacle is arranged to collect projectiles of which a         trajectory is deviated by the inclined transparent interactive         surface.

Also optionally, the receptacle includes a damping material and is removably mounted and/or as a pivot connection on the protective case.

Also optionally, a device for locating an impact according to the invention can comprise the electronic device connected to the electronic central unit and at least one of said calculators can be integrated into the calculating means of the electronic device.

Also optionally:

-   -   a divergent lens is interposed between the display screen of the         electronic device and the transparent interactive surface, when         said at least one portion of the electronic device is inserted         into the protective case and when the positioning of the display         screen is adjusted, and     -   a rear projection sheet is spread over an inner face of the         transparent interactive surface.

The invention shall be better understood using the following description, provided solely as an example and in reference to the accompany drawings wherein:

FIGS. 1 and 2 diagrammatically show as front and side views the general structure of a device for locating an impact according to a first embodiment of the invention,

FIGS. 3 and 4 diagrammatically show as side views the general structure of a device for locating an impact according to a second embodiment of the invention,

FIGS. 5 and 6 diagrammatically show as front and side views the general structure of a device for locating an impact according to a third embodiment of the invention,

FIG. 7 diagrammatically shows as a side view the general structure of a device for locating an impact according to a fourth embodiment of the invention, and

FIG. 8 diagrammatically shows as a side view the general structure of a device for locating an impact according to a fifth embodiment of the invention.

The device for locating an impact diagrammatically shown as front and side view in FIGS. 1 and 2 comprises a protective case 10 of which a front face is comprised of a transparent interactive surface 12 able to propagate progressive mechanical waves from an impact P.

Four transducers PT_(A), PT_(B), PT_(C) and PT_(D) are arranged and distributed against the transparent interactive surface 12, more precisely at the four corners of the rectangle that it forms. They are designed to capture the progressive mechanical waves propagating in the interactive surface 12 and to transform them into electrical signals. They are connected to an electronic central unit 14, for example fastened to the bottom of the protective case 10, of which a calculator receives their electrical signals and is programmed to identify instants of impact P detection in the electrical signals received. The electronic central unit 14 further comprises a calculator programmed to locate the impact P in the transparent interactive surface 12 by analysing time differences of propagation of progressive mechanical waves from the impact P to the transducers PT_(A), PT_(B), PT_(C) and PT_(D) on the basis of the instants of impact detection identified. The two aforementioned calculators may form only one, the distinction being purely functional. They can have the form of one or several microprocessors programmed to carry out a certain number of functions that can be implemented using computer programs, i.e. in the form of a computer device. But these functions could also be at least partially micro programmed or micro wired in dedicated integrated circuits. Thus, alternatively, the computer device implementing the aforementioned calculators could be replaced with an electronic device comprised solely of digital circuits (without a computer program) for the carrying out of the same functions.

Note in addition that, generally, the transparent interactive surface 12 is of any shape, not necessarily rectangular. The number of transducers is also indifferent, at least equal to three in order to allow for a locating by analysis of the time differences of propagation as taught in document U.S. Pat. No. 6,367,800 B1.

In accordance with a possible embodiment of the invention, the protective case 10 has an interior volume intended to receive an electronic device 16 with a display screen 18 in an arrangement according to which the display screen 18 is placed facing the transparent interactive surface 12. Advantageously, the transducers PT_(A), PT_(B), PT_(C) and PT_(D) are arranged in such a way as to not to be in the zone of the display screen 18. The protective case 10 has an opening 20 through which the electronic device 16, for example a mobile telephone or a digital tablet, can be inserted. Optionally, it can further comprise a closure element of the opening 20, in particular and hermetic closure element for use outdoors or even under water. It is advantageously dimensioned, in size and in format, to adapt precisely to the dimensions of the electronic device 16 that it is intended to receive.

Means 22 for adjusting a positioning of the display screen 18 with respect to the transparent interactive surface 12, for a centring of the display screen 18 on a mark R linked to the transparent interactive surface 12, are provided in the protective case 10. This centring of the display screen 18 on the mark R includes a complete resetting of the marks of the display screen 18 on the marks of the transparent interactive surface 12. In theory, there are six degrees of freedom (three degrees of freedom in translation and three degrees of freedom in rotation), in such a way that the centring includes by default a control of these six degrees of freedom using the means for adjusting 22. In the simplified example of FIG. 1, they are mechanical, more precisely in the number of four, integral with the four lateral walls of the protective case 10 and formed of spring and shim systems, for a centring according to only two degrees of freedom (horizontal and vertical directions). Indeed, it is supposed in this simple example that the plane of the display screen 18 remains parallel to the plane of the transparent interactive surface 12, that their edges remain parallel and that the distance that separates them remains constant. According to the design constraints of the protective case 10 and of the targeted applications, the means for adjusting 22 can be designed in the form of any known equivalent means for adjusting that are controlled manually or electronically, such as screw and nut systems, cylinders or others.

The mark R is for example of a very fine marking of diagonals, of which the ends are for example centred on the transducers PT_(A), PT_(B), PT_(C) and PT_(D), on the transparent interactive surface 12, but it can also be another type of marking, for example at least one simple cross marking at least one point, for example located at the centre of the front face of the protective case 10, more or less discrete and to be defined according to the design constraints of the protective case 10. An embedded software in the electronic device 16 can then position a visual marker on the display screen 18 in correspondence with the marker R during an initialisation executed after positioning. This initialisation advantageously allows for a geometrical calibration of the transparent interactive surface 12 with respect to the display screen 18.

Thus the means for adjusting 22 associated with a geometrical calibration allow for the insertion and maintaining of a large variety of electronic devices with a display screen (telephones, tablets, computers, etc.), making the protective case 10 adaptable to several screen sizes and formats.

Although a geometrical calibration on two marked diagonals or a single central marking can be considered in the simplified example of FIG. 1, in the general case it may be necessary to mark several points on the transparent interactive surface 12, in particular at least three marked unaligned points in order to carry out the centring calibrated over six degrees of freedom. According to an alternative embodiment, the embedded software in the electronic device 16 mentioned hereinabove can then be designed to position at least three visual markers respectively on these marked points, with the mouse, using the directional arrows on a keyboard, using a control or any other known equivalent interactive tool. After positioning of these markers, the calibrated centring of the display screen 18 over the transparent interactive surface 12 by resetting their respective marks can be carried out easily through calculation. Such a centring carried out by software can advantageously supplement, and even replace, a mechanical adjustment. In this latter case, the mechanical means for adjusting 22 can be replaced with means for adjusting that combine markings and software calculations, integral with the protective case 10 in that they comprise the markings carried out on the transparent interactive surface 12.

The transparent interactive surface 12 is advantageously designed in a material of sufficient rigidity, in particular polycarbonate, so that the impact P does not significantly affect the display screen 18 of the electronic device 16 when the positioning of the display screen 18 is adjusted, in particular for an impact of a few joules. Moreover, it should be noted that it also makes it possible to make use of all of the resources of the electronic device 16, such as its possible embedded camera(s), microphone(s), speaker(s), as well as its display screen 18 and its capacities for accessing the Internet, for optimised interactivity with visual and sound animations according to the applications considered (leisure, sports or others).

Finally, the electronic central unit 14 comprises a calculator programmed to convert the location of the impact P in the transparent interactive surface 12 into a location of the impact P in the display screen 18 when the electronic device 16 is inserted into the protective case 10 and when the positioning of the display screen 18 is adjusted using the means 22. As hereinabove, this calculator can be different from the two aforementioned calculators or form only one with them, with the distinction being purely functional. It can also be implemented indifferently in a computer or electronic device.

When the electronic device 16 is inserted into the protective case 10, it is advantageously connected to the electronic central unit 14, for example via a USB (“Universal Serial Bus”) connection or other. Thus, the electronic central unit 14 can transmit the results of its calculations to the electronic device 16. Thus also, the electronic device 16 can supply the electrical power required for the operation of the electronic central unit 14, although the latter can have its own autonomous and rechargeable source of electrical energy for example integral with the protective case 10.

Alternatively, note that all or a portion of the aforementioned calculators can be offset in the electronic device 16 which itself has its own means of calculation. For example, the electronic central unit 14 may contain none of the aforementioned three calculators, in which case it simply transmits the signals that it receives from the transducers PT_(A), PT_(B), PT_(C) and PT_(D) to the electronic device 16 for processing, after possibly amplifying them and comparing them to predetermined thresholds, then digitising. Also for example, the electronic central unit 14 may comprise only the first of the three aforementioned calculators, in which case it transmits the instants of impact P detection that it has identified to the electronic device 16 so that it calculates itself the location of this impact P. Also for example, the electronic central unit 14 can comprise only the first two of the three aforementioned calculators, in which case it transmits the location of the impact P that it has calculated in the transparent interactive surface 12 to the electronic device 16 so that it converts it itself into a location in the display screen 18.

Also note that one of the aforementioned calculators can estimate a power of the impact P in addition to its location, by simple integration of the signals received by the electronic central unit 14.

Also note that the protective case 10 can comprise conventional fastening elements 24 at the rear, for a fastening against a vertical support. Generally, it can easily be transported with the electronic device 16 with a display screen 18 when the latter is precisely positioned and fastened using the means for adjusting 22.

In another embodiment of the invention shown diagrammatically in FIGS. 3 and 4 as side views, the device for locating an impact has a front face inclined towards the front, for example by a non-zero angle between 5 and 25 degrees, with respect to the bottom of the protective case 10, in such a way as to have this same inclination with respect to the vertical when the protective case 10 is arranged on a stable support. In this way, the transparent interactive surface 12 is inclined by the same angle. On the other hand, the electronic device 16 once inserted and positioned in the protective case 10 has to be in an arrangement such that its display screen 18 remains vertical in order to facilitate the visibility thereof by a user. This results in a parallax error that can be corrected, using knowledge of this inclination, in the calculation for converting the location of the impact P. Thus, in a use of the device for locating an impact according to which the impact P is generated by a shooting of a projectile, this non-zero angle makes it possible to deviate the trajectory of the projectile by preventing any bouncing able to injure the user.

Optionally and advantageously, a receptacle 26 can furthermore be arranged in the lower portion of the transparent interactive surface 12, with this receptacle 26 including a damping material 28, for example a foam panel, to collect the projectiles deviated by the front face of the protective case 10. It can furthermore be conformed to adapt as a cover to the dimensions of the transparent interactive surface 12 in a storage position of the device for locating an impact. It can be removably mounted and/or as a pivot connection on the protective case 10. It is shown in the deployed position ready for use in FIG. 3 and in storage position, closed against the transparent interactive surface 12, in FIG. 4.

In another embodiment of the invention shown diagrammatically in FIGS. 5 and 6 as front and side views, the device for locating an impact comprises a protective case 30 conformed to receive a keyboard support 32 of a portable computer 34 further comprising a support 36 for a flat display screen 38 with a pivot connection with the keyboard support 32. To this effect the rear face 40 of the protective case 30 has an opening through which the keyboard support 32 can be inserted. The protective case 30 is integral, via the upper tranche of its rear face 40, with a transparent interactive surface 42 that extends upwards according to a non-zero angle, for example between 5 and 25 degrees, with respect to the vertical. The transparent interactive surface 42 is dimensioned to correspond to the dimensions of the display screen 38 of the portable computer 34. It is moreover arranged to be facing the display screen 38, the latter having advantageously to remain vertical for better visibility by a user, when the keyboard support 32 is correctly inserted and positioned in the protective case 30. This results, as in the preceding example, in a parallax error that can be corrected, using knowledge of this inclination, in the calculation for converting the location of the impact P. For better control of the inclination with respect to the vertical and of the correction of parallax error, a shim 43 can be arranged between the inclined transparent interactive surface 42 and the display screen 38 thus maintained vertical.

The transparent interactive surface 42 is as hereinabove provided with four transducers PT_(A), PT_(B), PT_(C) and PT_(D) and with the mark R. As for the protective case 30, it comprises as in the preceding example an electronic central unit 44 connected to the four transducers PT_(A), PT_(B), PT_(C) and PT_(D) and connected to the portable computer 34, as well as means 46, 48, 50 for adjusting a positioning of the keyboard support 32 in the protective case 30 for a centring of the display screen 38 on the mark R of the transparent interactive surface 42. In the example of FIGS. 5 and 6, these means for adjusting comprise a plateau 46, intended to receive the keyboard support 32, adjustable in height using an endless screw system 48, and two lateral systems 50 with springs and shims for a horizontal centring. A locknut can also be provided in order to ensure a locking of the positioning of the display screen 38 when the latter is correctly arranged with regards to the mark R.

Optionally and advantageously shown in FIG. 6, a receptacle 52 can furthermore be arranged above the protective case 30 in front of the transparent interactive surface 42, with this receptacle 52 including a damping material 54, for example a foam panel, to collect the projectiles deviated by the transparent interactive surface 42.

Another embodiment of the invention shown diagrammatically in FIG. 7 as a side view differs from the first embodiment of FIGS. 1 and 2 in that a divergent lens 56 is interposed between the display screen 18 of the electronic device 16 and the transparent interactive surface 12 and in that a rear projection sheet 58 is spread over the inner face of the transparent interactive surface 12. This makes it possible to use an electronic device 16 with a display screen 18 of small size (for example a mobile telephone or a digital tablet) in a protective case 10 of large size with a wide transparent interactive surface 12. The images displayed on the display screen 18 are indeed enlarged by the divergent lens 56 in order to be adapted to the size of the transparent interactive surface 12. A lens with a short focal length is preferably used in order to have a protective case 10 with the least depth possible. The disadvantage with this type of lens is the deformation of the image, but is can be compensated via software such as is commonly practised for certain video projectors. With regards to the rear projection sheet, this can be a single sheet of tracing paper or a sheet with better performance such as exits in a manner known per se in the market. In order to ensure effective rear projection on this sheet, the protective case 10 is advantageously opaque.

Optionally and advantageously as in the two preceding embodiments, the transparent interactive surface 12 can be inclined towards the front and a receptacle with damping material can be arranged in front, in order to collect the projectiles deviated by the transparent interactive surface 12.

Another embodiment of the invention shown diagrammatically in FIG. 8 as a side view differs from the embodiment of FIG. 7 in that the electronic device 16 of the mobile telephone type or a digital tablet is replaced with a video projector 60. This solution is possible because there are today highly compact video projectors at a reduced cost. In this case, the divergent lens 56 is not necessary since one is integrated into the video projector 60. The latter is advantageously connected to a USB port 62 arranged at the bottom of the case 10 that allows it an electrical connection to a computer or a digital tablet. Such a connection can supply it with electrical energy. It can also have an autonomous electrical power in the case or by connection to the mains. Finally, the correct positioning of the video projector 60 with respect to the mark R of the transparent interactive surface 12 can be done at the time of manufacture, but it is also advantageously adjustable using the means 22.

Other embodiments not shown can be considered. In particular the protective case can be conformed to receive in its interior volume a support for a flat screen for a portable computer, a monitor for computer or a television receiver.

With all of these embodiments possible, multiple applications, leisure or sports or others, can be imagined, such as:

-   -   a musical application: using drumsticks and a device for         locating an impact according to the invention into which a         connected electronic device such as a smartphone or a digital         tablet is inserted, this connected electronic device can be         transformed into a simulator of a set of drums, xylophone or         other percussion instrument; each located and calibrated impact         emits a sound as if the user had a real percussion instrument;         the user can also be guided by suggesting sequentially to him         via the display screen the zones to be reached and the force of         the impact; for increased realism, the user can use a smartphone         in order to simulate a first musical instrument and a digital         tablet in order to simulate a second musical instrument, with         the two pieces of equipment able then to be connected via a         Bluetooth connection,     -   a game of arrows or darts: the device for locating an impact is         hung on a wall, with the players able to use real arrows or         darts with a protection at the end or simple pens; the display         screen of the electronic device arranged in the protective case         displays a dart target and, when an impact is located, the         virtual image of the arrow or dart planted at the location where         the impact was detected is superimposed on the image of the         target; it is then possible to count the points and optionally         identify the players and their approximate distance via the         camera of the electronic device via image processing,     -   a shooting game: the display screen of the electronic device         arranged in the protective case can display an active scene, for         example a flying duck; using a ball gun, a player can reach the         duck which causes for example an animation and a counting of         points; several connected electronic devices can also be used         for more interactivity (digital tablet in front of the player an         behind him, etc.); in a multi-player mode it is possible to use         projectiles of different natures so as to identify via the         impact signature the various players and thus their respective         actions on the same interactive surface,     -   etc.

It clearly appears that a device for locating an impact such as one of those described hereinabove makes it possible to combine at least cost and in complete safety the simplicity and the resistance of a device for locating an impact with progressive mechanical wave detection with the possibilities of visual and sound interactivities offered by an electronic device, in particular an electronic device connected to the Internet. It is furthermore potentially autonomous and transportable.

Note moreover that the invention is not limited to the embodiments described hereinabove. It will appear to those skilled in the art that various modifications can be made to the embodiments described hereinabove, in light of the teaching that has just been disclosed to them. In the claims that follow, the terms used must not be interpreted as limiting the claims to the embodiments disclosed in this description, but must be interpreted so as to include therein all of the equivalents that the claims aim to cover due to their formulation and of which the foreseeing is within the scope of those skilled in the art by applying their general knowledge to the implementing of the teaching that has just been disclosed to them. 

1. A device for locating an impact against a transparent interactive surface able to propagate progressive mechanical waves from the impact, comprising: the transparent interactive surface against which are arranged and distributed at least three transducers designed to capture the progressive mechanical waves propagating in the transparent interactive surface and to transform them into electrical signals, an electronic central unit, connected to the transducers in order to receive their electrical signals, a calculator programmed to identify instants of impact detection in the electrical signals received by the electronic central unit, and a calculator programmed to locate the impact in the transparent interactive surface by analysing time differences of propagation of progressive mechanical waves from the impact to the transducers on the basis of the instants of impact detection identified, characterised in that it further comprises: a protective case integral with the transparent interactive surface and of which the interior volume is intended to receive at least a portion of an electronic device with a display screen in an arrangement according to which the display screen is placed facing the transparent interactive surface, the protective case having an opening through which said at least one portion of the electronic device can be inserted, means, integral with the protective case, for adjusting a positioning of the display screen with respect to the transparent interactive surface for a centering of the display screen on a marker carried out by a marking on the transparent interactive surface, and a calculator programmed to convert the location of the impact in the transparent interactive surface into a location of the impact in the display screen when said at least one portion of the electronic device is inserted into the protective case and when the positioning of the display screen is adjusted.
 2. The device for locating an impact according to claim 1, wherein the protective case is shaped in such a way as to receive in its interior volume one of the elements of the set formed of a mobile telephone, a digital tablet, a flat screen support for portable computer, a keyboard support for portable computer, a monitor for computer, a television receiver and a video projector associated with a rear projection screen.
 3. The device for locating an impact according to claim 1, wherein the transparent interactive surface is designed in a material of sufficient rigidity, in particular polycarbonate, so that the impact does not significantly affect the display screen of the electronic device when the positioning of the display screen is adjusted.
 4. The device for locating an impact according to claim 1, wherein one of the walls of the protective case comprises the transparent interactive surface and the interior volume of the protective case is intended to receive at least the display screen of the electronic device.
 5. The device for locating an impact according to claim 4, comprising a closure element of the opening through which the display screen can be inserted, in particular a hermetic closure element.
 6. The device for locating an impact according to claim 1, comprising: an autonomous and rechargeable source of electrical energy integral with the protective case, or means of electrical connection to the electronic device, for an electrical power supply of the electronic central unit which is integral with the protective case.
 7. The device for locating an impact according to claim 1: wherein the transparent interactive surface is designed in such a way as to have an inclination towards the front by a non-zero angle with respect to the vertical when the protective case is arranged on a stable support, and further comprising a receptacle which is arranged to collect projectiles of which a trajectory is deviated by the inclined transparent interactive surface.
 8. The device for locating an impact WPM according to claim 7, wherein the receptacle includes a damping material and is removably mounted and/or as a pivot connection on the protective case.
 9. The device for locating an impact according to claim 1, comprising the electronic device connected to the electronic central unit and wherein at least one of said calculators is integrated into the means for calculation of the electronic device.
 10. The device for locating an impact according to claim 1, wherein: a divergent lens is interposed between the display screen of the electronic device and the transparent interactive surface, when said at least one portion of the electronic device is inserted into the protective case and when the positioning of the display screen is adjusted, and a rear projection sheet is spread over an inner face of the transparent interactive surface. 